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What is a stem cell transplant?

Reasons for a stem cell transplant

One goal of a stem cell transplant is to replace unhealthy, failing or insufficient stem cells with normal stem cells.  Another goal is to use donor stem cells to provide a source of healthy cells to make up for abnormal body chemical functions. A third goal is to use a person’s own stem cells to overcome the effects of cancer and chemotherapy. Normal stem cells are taken from a donor (can be from a family member or an unrelated individual or the patient).  When stem cells are received from another person (allogeneic transplant), the stem cells may identify the patient’s body as foreign and may work to attack it.  Therefore, the body must be prepared to accept the new marrow.  A conditioning regimen, or treatment, is given in the form of chemotherapy, radiation, or both.  This regimen empties the stem cells space, kills any residual cancer cells and turns off the immune system to prevent an attack on the patient’s body.  The conditioning regimen allows the stem cells to accept the new body.  Eventually the new stem cells will begin to make healthy blood cells in the stem cells space and slowly the immune system will return to normal functioning.

Until the new marrow produces healthy blood cells, your child will require support through red cell transfusions, platelet transfusions, and antibiotics. Your child’s immune system will not be able to fight infections initially because the immune system was suppressed or turned off during the conditioning regimen.  Special precautions will need to be taken to prevent or treat infections until the immune system is able to effectively fight infections.

Engraftment occurs when the new stem cells begin producing healthy blood cells in the stem cells.  This is first observed by a rise in your child’s white blood cell count.  Once your child’s absolute neutrophil count (ANC) is greater than 500 for three consecutive days engraftment has occurred.  This is different from donor cell recovery; a blood test called Chimerism is sent once the patient has engrafted. The chimerism report shows what percentage of donor cells are in the blood sample. Ideally, in many diseases such as cancer, the chimerism should be 100% donor.  After engraftment, your child will gradually need fewer transfusions as the new marrow is able to produce red blood cells and platelets.  Complete recovery of the immune system occurs when the new lymphocytes begin to function normally.  This may take six months to one year after transplant. Special blood tests indicate when recovery of the immune system occurs.  After the immune system has recovered, your child will need to repeat the recommended childhood immunizations.

Other Body Organs

Chemotherapy and radiation may affect the function of other body organs, such as the kidneys and liver.   The function of your child’s different body organs is evaluated before, during and after the transplant.  For further information, please see the section on preparing for the transplant.